Carbon-graphite composites comprising laminates of graphite or carbon fibers and a carbon matrix prepared from epoxy, phenolformaldehyde, or like resin are well known in the art.
This invention relates to a laminated artificial graphite article, more particularly, to a graphitized carbon fiber-mesophase composite.
Graphite is a material which is a good conductor of heat and electricity, extremely resistant to high temperatures, and also highly resistant to attack by most chemical reagents. Accordingly, graphite is an extremely important and useful material in industry in a great variety of applications.
Almost all the artificial graphite which is made today is prepared according to the teaching first set forth by E. G. Acheson in 1896. Acheson's process, which was the first successful process for the commercial production of artificial graphite articles, has been somewhat modified since that time. As a general rule, artificial graphite articles are fabricated from petroleum coke base material. This process comprises intimately mixing coke particles with a coal tar or pitch binder and forming the mixture. The resultant shaped articles are baked at about 1000.degree.C. and subsequently graphitized at 2500.degree.C. to 3000.degree.C. in an electric furnace.
When the above method is followed, a shaped graphite article is produced, or a graphite stock is produced, which can be shaped into the desired article by machining or other similar physical process.
The graphitized composites of this invention are espcially useful for their primary structural properties, particularly high temperature applications, as for example over 1000.degree.C. These uses can include space, re-entry, and suborbital flight applications, and the like. They can also be used to fabricate dies for hot molding operations in the preparation of ceramics and the like.
Additionally, for use as a moderator in nuclear reactors, graphite is used to slow down fast neutrons through collision of these fast neutrons, produced in the fission of U-235 atoms, with the moderator. The neutrons being moderated should spend the minimum possible time in the intermediate energy region where they are liable to be captured by the more abundant U-238 atoms and be lost to the system without producing further fission. A high density graphite moderator increases the compactness of the reactor. Therefore, composites of high density, approaching the theoretical density of carbon, 2.25 g/cm.sup.3, are desired.
More recently, a process has been devised for preparing a very high density graphite by heating a liquefiable hydrocarbon e.g. a coker feedstock, to a temperature of at least 400.degree.C. to form a fusible substance containing at least 75 percent by weight of mesophase, carbonizing the mesophase therefrom at about 400.degree.C. to 500.degree.C. and converting the resulting body to graphite by conventional graphitization techniques at temperatures of up to 3000.degree.C.